Milk thistle - also known by its Latin name silybum marianum - is a herbal product traditionally used to relieve symptoms associated with occasional over indulgence of food and drink, such as indigestion and upset stomach.
Silymarin, an antioxidant, is the main active ingredient in milk thistle. It is extracted from the seeds of the plant, which is native to Southern Europe, Russia, Asia Minor and North Africa.
Milk thistle is one of the eight most popular herbal ingredients in the UK.
Some milk thistle products are registered with the UK medicines regulator, the Medicines and Healthcare products Regulatory Agency (MHRA) under the Traditional Herbal Registration (THR) scheme. This does not mean the regulator has tested products that contain it to prove it works or that claims about it have been verified by clinical studies. However, it does mean milk thistle has been confirmed as being used as a traditional medicine for at least 30 years - and 15 years in the EU.
Registration also confirms the product manufacturer is meeting established standards of safety and quality.
Milk thistle is not associated with any significant side effects. However, it can cause diarrhoea and may lead more rarely to nausea, bloating, excessive wind and upset stomach.
Women who are breastfeeding or pregnant should avoid using milk thistle. Seek medical advice if you are suffering from liver disease before taking milk thistle.